Surface treated aramid fibers and a process for making them

Abstract

The invention relates to highly processable, hydrophobic aramid fibers of high modulus, improved surface frictional properties, scourability, low abrasion depositing, low fibrillation obtainable by surface reaction of an aromatic polyamide fiber with a surface reactant comprising a ketene dimer (R1R2C2O)(R1R2C2O)(I). The invention further relates to a process for the production and the use of said fibers.

I claim: 
     
       1. An aramid fiber having a surface coated by a reaction product of the aramid and a surface reactant wherein the reaction product was formed at the surface of a never-dried aramid fiber, wherein the surface reactant was applied to the aramid fiber while the aramid was swollen with 15 to 200 percent water, the reaction product was formed, and the coated aramid fiber was dried, and wherein the surface reactant comprises a ketene dimer of the general formula   [R.sup.1 R.sup.2 C.sub.2 O]·[R.sup.1' R.sup.2' C.sub.2 O](I)     wherein each of the groups R 1  and R 1' , which may be same or different, represents an alkyl, cycloalkyl, aryl, alkenyl, aralkyl, aralkenyl, or alkaryl, having from 4 to 32 carbon atoms; and each of the groups R 2  and R 2' , which may be same or different, represents a hydrogen atom or an alkyl or alkenyl group having from 1 to 6 carbon atoms.   
     
     
       2. A fiber according to claim 1 wherein groups R 1 , R 1'  in formula (I) are alkyl or alkenyl and have from 8 to 24 carbon atoms. 
     
     
       3. A fiber according to claim 2 wherein the groups R 1 , R 1'  in formula (I) are octyl, decyl, dodecyl, tetradecyl, hexadecyl, octadecyl, eicosyl, docosyl, tetracosyl, tetradecenyl, hexadecenyl, octadecenyl, eicosenyl, docosenyl, and tetracosenyl groups. 
     
     
       4. A fiber according to claim 1 wherein the groups R 2 , R 2'  in formula (I) are C 1  -C 3  -alkyl, C 1  -C 4  -alkenyl, or hydrogen. 
     
     
       5. A fiber according to claim 1 wherein the ketene dimer is tetradecyl, tetradecenyl, hexadecyl, hexadecenyl, eicosyl, or eicosenyl ketene dimer. 
     
     
       6. A fiber according to claim 1, wherein the amount of the surface reactant on the fiber is 0.05 to 8.0% by weight. 
     
     
       7. A fiber according to claim 1, characterized in that the aramid is made from repeating units having the general formula   (--NH--A.sub.1 --NH--CO--A.sub.2 --CO--).sub.n     wherein A 1  and A 2  are selected from the group consisting of substituted aromatic, unsubstituted aromatic, polyaromatic, and heteroaromatic rings.   
     
     
       8. A fiber according to claim 7 characterized in that A 1  and A 2  are independently from each other selected from 1,4-phenylene, 1,3-phenylene, 1,2-phenylene, 4,4'-biphenylene, 2,6-naphthylene, 1,5-naphthylene, 1,4-naphthylene, phenoxyphenyl-4,4'-diylene, phenoxyphenyl-3,4'-diylene, 2,5-pyridylene and 2,6-quinolylene and which may or may not be substituted by one or more substituents comprising halogen, C 1  -C 4  -alkyl, phenyl, carboalkoxyl, C 1  -C 4  -alkoxyl, acyloxy, nitro, dialkylamino, thioalkyl, carboxyl and sulfonyl and in which the --CONH--may be replaced by a carbonylhydrazide-, azo- or azoxy-group. 
     
     
       9. A fiber according to claim 7, characterized in that the aramid is poly-m-phenylene-isophthalamide. 
     
     
       10. A fiber according to claim 7, characterized in that the aramid is poly-p-phenylene-terephthalamide.